The crane's history: from treadle wheel to hydraulics

The need to lift heavy loads is as old as construction itself. As long as people have stacked stone on stone, they have sought ways to move more than a group of men could carry in their hands. The crane is the answer to that need — a machine that for more than two and a half thousand years has made it possible to hoist and place loads that far exceed human muscle power. The story of the crane is the story of how we have learned to multiply our own strength through wheels, ropes and later through engine power.

§Antiquity: the Greeks and Romans invent the lever

The first real lifting crane is attributed to the ancient Greeks. As early as the end of the 5th century BC, characteristic indentations are found on the blocks in Greek temples, located just above the stone's centre of gravity — traces of the tongs and lifting lugs a crane gripped. It shows that by that time they had stopped pulling stones up ramps and instead lifted them vertically with a machine that could multiply the force.

The Romans took over the Greeks' crane and developed it further as construction grew in the Empire. They built an entire family of cranes that differed by how many disks were in the pulley block. The simplest, trispastos, had three disks, so one man at the winch could lift about 150 kg. The most powerful, polyspastos, had multiple masts and a set of three times five disks — and when four men operated the winch, it could lift up to 3,000 kg.

The Romans' greatest innovation was the treadmill. Instead of a hand winch, men walked inside a large wooden wheel, and the wheel's diameter provided a powerful lever arm. A treadmill crane could with this trick lift far more than a hand-operated crane — estimated at up to 6,000 kg. The principle was so effective that it became the foundation of crane building for more than a millennium.

§The Middle Ages: the treadwheel raises the cathedrals

When the Western Roman Empire fell much of Roman building technology was forgotten in Western Europe. The treadwheel crane first appeared again in written sources around the beginning of the 1200s — and this time it was used on a large scale to build the Gothic cathedrals. Large treadwheels were hoisted right up into the roof construction where they stood lifting stones beams and lead roofs to the dizzying heights the cathedrals reached. Several of these medieval cranes are still preserved today in church towers around Europe.

The materials were wood and hemp: the frame and wheel in oak the rope woven from hemp and the pulleys cut in hard wood. The crane was typically powered by human force in the wheel but also by horses and by hand winches with pole and lever that held the load when you let go. Safety depended entirely on the craftsmen's experience — there were neither load diagrams marked working load nor inspections in the sense we know today.

§Industrialisation: steam, iron and the first stationary cranes

With industrialisation in the 1800s the crane changed radically. Two things drove development: iron and steel replaced wood and the steam engine replaced human and horse power. The steam crane could work without tired legs in a wheel and lift faster and heavier and quickly became indispensable at ports railways and in the new factory halls. In workshops and warehouses came travelling cranes and portal cranes — fixed cranes that ran on rails and could cover an entire area.

It was also in this period that heavy accidents really became visible. When the power grew so did the consequences of a break or overload. It was the start of a gradual buildup of rules inspections and requirements for material strength — a development that has continued ever since.

§20th century: electric motor mobile crane and hydraulics

Around the year 1900, steam began to give way to petrol and diesel motors as well as electric motors. The first self-propelled mobile cranes appeared around World War I: cranes mounted on a vehicle with rubber wheels or caterpillar tracks that could drive to the job instead of being built on site. This made the crane flexible in a completely new way.

The really big leap came with hydraulics, which was developed and spread in the wake of World War II. Hydraulic cylinders could raise and extend a boom with a precision and force that mechanical cables could not match, and in the 1960s came the first fully telescoping hydraulic booms. At the same time, the company Liebherr invented the modern tower crane in 1949 with a rotating tower and horizontal arm, which has since defined construction sites around the world.

§The crane today: power controlled by rules and electronics

Today's cranes are both far more powerful and far more monitored than ever before. The largest mobile cranes can lift hundreds of tons and extend their booms many tens of thousands of times higher than a medieval crane. But the raw power is now framed by a web of safety: the load diagram that tells precisely what the crane may lift at a given boom length and angle; the electronic overload protection that intervenes before the limit is exceeded; the daily inspection and the statutory main inspection and the requirement for certification and training before anyone is allowed to operate the crane.

Where the medieval master builder relied on his experience and his eye, today's crane operator relies on calculated limits, marked equipment and documented inspections. That is the most important difference between then and now — not just that cranes have become stronger, but that safety has gone from being a single person's sense to being a shared, written system. The basic principles the Romans knew still apply; it is the framework around them that has become a profession.

“Give me a fixed point and I will move the Earth — the ancient idea of multiplying your own strength is still the core of every crane lift.”